1. Field of the Invention
This invention relates to covalently linked polypeptide cell modulators, each of which acts through a different and specific cell receptor to initiate complementary biological activities. Polypeptide cell modulators include lymphokines, monokines, interferons, polypeptide hormones or cytotoxins as well as modifications and active segments of such peptides. Also described are DNA sequences, plasmids and hosts capable of expressing the linked polypeptide cell modulators.
2. Description of Prior Art
One class of polypeptide cell modulators can be defined whose members exert an antiproliferative effect almost specifically on tumour cells and possess immunomodulatory activity, but lack antiviral activity. Among the members of this class are human lymphotoxin and tumour necrosis factor (Gray, P. W. et al. Nature 312, 721, 1984; Pennica D. et al. Nature 312, 724, 1984).
Human lymphotoxin (hLT) is a cytotoxin induced in lymphocytes by a specific antigen or by bacteria or parasites and has a cytotoxic or cytostatic action on a variety of tumour cells in vivo or in vitro. hLT has been implicated to play a role in cell-mediated immunity and its potent anti-tumour effect suggests it may be of value therapeutically (Ruddle, N. H. et al. Lymphokine Res. 2, 23, 1983).
Another class of lymphokine can be defined whose members induce an antiviral state in responsive cells, and also have antiproliferative and immunomodulating activity. Among the members of this class are leukocyte interferon (IFN-alpha), fibroblast interferon (IFN-beta) and immune interferon (IFN-gamma).
It has been reported that mixtures of type I interferons (IFN-beta or IFN-alpha) and type II interferons (IFN-gamma) are highly synergistic in exerting an antiviral or antiproliferative effect. (Fleishmann, W. R. et al. Infect. Immun. 26, 248, 1979; Czarniecki, C. W. et al. J. Virol. 49, 490, 1984).
In mixtures, much lower concentrations of type I and type II interferons can achieve a particular level of response. Several authors have also described IFN-gamma/hLT and IFN-alpha/hLT synergy or related synergies (Lee, S. H. et al. J. Immunol. 133, 1083, 1984; Stone-wolff, D. S. et al. J. Exp. Med. 159, 828, 1984; Williams, T. W. Lymphokine Res. 3, 113, 1984). European Patent Application (EPO 107 498), (EPO 128009).
However, in these instances, there was no disclosure of covalent linkage of the two classes of molecules that were synergistic.
Additional patent publications have described the primary amino acid sequences of human IFN-gamma (GB 2 107 718 A), the IFN-gamma (IFN X918) described herein (PCT 83/04053), IFN-alphas (U.S. Pat. No. 4 414 150-08.11.83) and IFN-beta (e.g. GB 0689 70B; GB 2098996A). A modified IFN-beta (IFN X430) described herein is identical to human fibroblast IFN-beta except that amino acids 36 to 48 inclusive are replaced with amino acids 34 to 46 inclusive from human IFN-alpha 1 (European Patent Application 85105914.7 and (Taniguchi, T. et al. Nature 285, 547, 1980).